nbd-server: Limit the number of connections

Hi there,

This is a patch that allows to limit the number of opened connections in
nbd-server.

This limitation can be specified from both command line and config
files:
- -M <n> or --max-connections <n> from command line
- or maxconnections = <n> in config files (export sections)

Regards,
Greg

diff --git a/man/nbd-server.1.in.sgml b/man/nbd-server.1.in.sgml
index c9190b0..7b7f185 100644 (file)
--- a/man/nbd-server.1.in.sgml
+++ b/man/nbd-server.1.in.sgml
@@ -66,6 +66,7 @@ manpage.1: manpage.sgml
       <arg><option>-l <replaceable>host list filename</replaceable></option></arg>
       <arg><option>-o <replaceable>section name</replaceable></option></arg>
       <arg><option>-C <replaceable>config file</replaceable></option></arg>
+      <arg><option>-M <replaceable>max connections</replaceable></option></arg>
     </cmdsynopsis>
   </refsynopsisdiv>
   <refsect1>
@@ -208,6 +209,13 @@ manpage.1: manpage.sgml
        </listitem>
       </varlistentry>
       <varlistentry>
+        <term><option>-M</option></term>
+       <listitem>
+         <para>Specify the maximum number of opened connections. If this
+         parameter is not specified, no limit is set.</para>
+       </listitem>
+      </varlistentry>
+      <varlistentry>
        <term><option>host list filename</option></term>
        <listitem>
          <para>This argument should contain a list of IP-addresses

diff --git a/man/nbd-server.5.in.sgml b/man/nbd-server.5.in.sgml
index f0aae0a..351fd80 100644 (file)
--- a/man/nbd-server.5.in.sgml
+++ b/man/nbd-server.5.in.sgml
@@ -596,6 +596,16 @@ manpage.1: manpage.sgml
          </para>
        </listitem>
       </varlistentry>
+      <varlistentry>
+       <term><option>maxconnections</option></term>
+       <listitem>
+         <para>Optional; integer</para>
+         <para>
+           If specified, then it limits the number of opened connections for
+           this export.
+         </para>
+       </listitem>
+      </varlistentry>
     </variablelist>
     
   </refsect1>

diff --git a/nbd-server.c b/nbd-server.c
index a11e37a..820458c 100644 (file)
--- a/nbd-server.c
+++ b/nbd-server.c
@@ -204,6 +204,7 @@ typedef struct {
        gchar* postrun;      /**< command that will be ran after the client
                                  disconnects */
        gchar* servename;    /**< name of the export as selected by nbd-client */
+       int max_connections; /**< maximum number of opened connections */
 } SERVER;
 
 /**
@@ -358,14 +359,15 @@ inline void writeit(int f, void *buf, size_t len) {
  */
 void usage() {
        printf("This is nbd-server version " VERSION "\n");
-       printf("Usage: [ip:|ip6@]port file_to_export [size][kKmM] [-l authorize_file] [-r] [-m] [-c] [-C configuration file] [-p PID file name] [-o section name]\n"
+       printf("Usage: [ip:|ip6@]port file_to_export [size][kKmM] [-l authorize_file] [-r] [-m] [-c] [-C configuration file] [-p PID file name] [-o section name] [-M max connections]\n"
               "\t-r|--read-only\t\tread only\n"
               "\t-m|--multi-file\t\tmultiple file\n"
               "\t-c|--copy-on-write\tcopy on write\n"
               "\t-C|--config-file\tspecify an alternate configuration file\n"
               "\t-l|--authorize-file\tfile with list of hosts that are allowed to\n\t\t\t\tconnect.\n"
               "\t-p|--pid-file\t\tspecify a filename to write our PID to\n"
-              "\t-o|--output-config\toutput a config file section for what you\n\t\t\t\tspecified on the command line, with the\n\t\t\t\tspecified section name\n\n"
+              "\t-o|--output-config\toutput a config file section for what you\n\t\t\t\tspecified on the command line, with the\n\t\t\t\tspecified section name\n"
+              "\t-M|--max-connections\tspecify the maximum number of opened connections\n\n"
               "\tif port is set to 0, stdin is used (for running from inetd)\n"
               "\tif file_to_export contains '%%s', it is substituted with the IP\n"
               "\t\taddress of the machine trying to connect\n" 
@@ -415,6 +417,7 @@ SERVER* cmdline(int argc, char *argv[]) {
                {"config-file", required_argument, NULL, 'C'},
                {"pid-file", required_argument, NULL, 'p'},
                {"output-config", required_argument, NULL, 'o'},
+               {"max-connection", required_argument, NULL, 'M'},
                {0,0,0,0}
        };
        SERVER *serve;
@@ -431,7 +434,7 @@ SERVER* cmdline(int argc, char *argv[]) {
        serve=g_new0(SERVER, 1);
        serve->authname = g_strdup(default_authname);
        serve->virtstyle=VIRT_IPLIT;
-       while((c=getopt_long(argc, argv, "-C:cl:mo:rp:", long_options, &i))>=0) {
+       while((c=getopt_long(argc, argv, "-C:cl:mo:rp:M:", long_options, &i))>=0) {
                switch (c) {
                case 1:
                        /* non-option argument */
@@ -508,6 +511,9 @@ SERVER* cmdline(int argc, char *argv[]) {
                        g_free(serve->authname);
                        serve->authname=g_strdup(optarg);
                        break;
+               case 'M':
+                       serve->max_connections = strtol(optarg, NULL, 0);
+                       break;
                default:
                        usage();
                        exit(EXIT_FAILURE);
@@ -606,6 +612,8 @@ SERVER* dup_serve(SERVER *s) {
        if(s->servename)
                serve->servename = g_strdup(s->servename);
 
+       serve->max_connections = s->max_connections;
+
        return serve;
 }
 
@@ -705,6 +713,7 @@ GArray* parse_cfile(gchar* f, GError** e) {
                { "sdp",        FALSE,  PARAM_BOOL,     NULL, F_SDP },
                { "sync",       FALSE,  PARAM_BOOL,     NULL, F_SYNC },
                { "listenaddr", FALSE,  PARAM_STRING,   NULL, 0 },
+               { "maxconnections", FALSE, PARAM_INT,   NULL, 0 },
        };
        const int lp_size=sizeof(lp)/sizeof(PARAM);
        PARAM gp[] = {
@@ -755,6 +764,7 @@ GArray* parse_cfile(gchar* f, GError** e) {
                                lp[10].target=lp[11].target=
                                lp[12].target=&(s.flags);
                lp[13].target=&(s.listenaddr);
+               lp[14].target=&(s.max_connections);
 
                /* After the [generic] group, start parsing exports */
                if(i==1) {
@@ -1739,6 +1749,12 @@ int serveloop(GArray* servers) {
                        if(net) {
                                int sock_flags;
 
+                               if(serve->max_connections > 0 &&
+                                  g_hash_table_size(children) >= serve->max_connections) {
+                                       msg2(LOG_INFO, "Max connections reached");
+                                       close(net);
+                                       continue;
+                               }
                                if((sock_flags = fcntl(net, F_GETFL, 0))==-1) {
                                        err("fcntl F_GETFL");
                                }